In late years, along with demands for high performance and downsizing of apparatus to which heat exchangers of the above-mentioned type are applied, the heat exchangers have been required to be increased in heat exchange amount and further reduced in size and weight. For that reason, a fin tube-type heat exchanger improved in these matters is suggested (see Patent Documents 1 and 2, for example).
The heat exchanger disclosed in Patent Document 1 includes a plurality of plate-like fins arranged parallel to each other, and allow gas to flow therebetween; heat-transfer tubes with an external diameter D (3 mm≦D≦7 mm), which are perpendicularly inserted into the plate-like fins and allows working fluid to flow inside thereof, the tubes being arranged in rows in a row direction perpendicular to a gas-passing direction and also arranged in lines in a line direction that is the gas-passing direction; and cuts provided in faces of the plate-like fins and having openings opposed to the gas flow. A row pitch Dp in the row direction of the heat-transfer tubes is set in a range of 2D≦Dp≦3D. A line pitch Lp in the line direction of the heat-transfer tubes is set in a range of 2D≦Lp≦3.5D. A fin pitch Fp of the plate-like fins is set in a range of 0.5D≦Fp≦0.7D. This makes it possible to materialize a heat exchanger that is low in ventilation resistance and good in heat-transfer performance.
Patent Document 2 refers to a fin tube-type heat exchanger having a number of fins that are arranged at intervals substantially parallel to each other and allow fluid A to flow through spaces therebetween, and a number of heat-transfer tubes that are substantially perpendicularly inserted into the fins and allow fluid B flows inside thereof. Carbon dioxide is used as the fluid B of the fin tube-type heat exchanger in which an external diameter D of each the heat-transfer tubes is set in a range of 1 mm≦D<5 mm, a tube line pitch L1 in a flowing direction of the fluid A of the heat-transfer tubes is set in a range of 2.5D<L1≦3.4D, and a tube row pitch L2 in a perpendicular direction to the flowing direction of the fluid A is set in a range of 3.0D<L2≦3.9D. As a consequence, it is possible to provide a compact and high-voltage heat exchanger in which the balance of heat exchange amount and frost formation resistance is good, as compared to conventional fin tube-type heat exchangers. Furthermore, since carbon dioxide is used as the fluid B, the refrigerant is high-pressure and high-density. Pressure loss in the heat-transfer tubes therefore affects temperature change only a little, so that a large amount of heat exchange can be obtained.